In general, as a method of generating an ion in an ion source, for example, a method of acquiring the ion by causing discharge in gas has been known. In this case, a microwave or an electron beam may be used in order to cause the discharge.
Meanwhile, a technology that generates ions by using a laser is present. By an ion source that generates the ions by using the laser, a laser beam is collected and irradiated onto a solid target, an element contained in the target is vaporized and ionized by energy of the laser beam to generate plasmas, the ions contained in the plasmas are transported as the plasmas are, and the ions are accelerated while extracting an ion beam.
According to the ion source, the ions can be generated by irradiating the laser to the solid target and it is advantageous in generation of the multi-charged ion.
However, ions in every charge state coexist in the ions generated in the ion source as described above.
In this case, for example, a high-frequency acceleration linear accelerator is used at a rear end of the ion source to selectively transport only a necessary ion of a valence, but in an ion source by itself, ions of valences which are unnecessary cannot be removed.